Are you behind NAT?: Test whether you're working from behind a (NAT) Network address translation.
Speed Test: Check your DSL, T-1 or Cable connection speed.
Mac OS X
AFP548: Excellent site on OS X server setup and upkeep
MacEnterprise: IT professionals sharing OS X Client and Server info
Apple Mac OS IT Guy: Mac OS X System Administrator's Tips
MacWorld: Magazine's informative website; reviews and how-tos
PC Magazine: Expert Online Help
Vista Upgrade Advisor: CNET's scanner checks your Windows box
Smart Computing: Windows PC Tech support in plain english
windowsdevcenter: O'Reilly's site for everything Windows
Phone & Security Systems
All Wired Communications: San Francisco based company provides comunications solutions and cabling services.
Alternative Technologies: Focusing on nonprofit phone system needs
Cult of Mac: Part of the Wired Magazine Blog Network
Adobe Train the Teacher: Free creative Suite tools for teachers and Adobe CS user